Electrical devices, such as network testers, are often assembled in a chassis to form a package. Such packages provide many conveniences for users of the device, including protecting the circuits in the device from the environment and rough handling. Many electronic components of such electrical devices have an operating temperature limit, for example 110xc2x0 C. in the case of many semiconductor devices. If the operating temperature limit is exceeded, the component may cease to operate in a definable manner and, at the extreme, may be damaged beyond repair. Most semiconductor devices generate a certain amount of heat during operation. Many semiconductor devices can generate enough heat to causes the temperature of the semiconductor to exceeds the operating temperature limit. Traditionally, two methods have been used to dissipate heat in electrical devices: heat sinks and fans.
A heat sink is a device designed to lower the temperature of an electronic device by dissipating heat into the surrounding air. Heat sinks are generally made of an aluminum alloy and often have fins on a first side to increase the surface area of the heat sink. A second side of such heat sinks, shaped to mate with a component, are attach to component. Basically, a heat sink conducts heat away from a component into the fins which are cooled by convection, e.g. the heat is transferred to the ambient air.
If, as is generally the case with traditional packages, the heat sink is internal of the chassis, the heated air needs to be exhausted to maintain the cycle of heat transfer from the heat sink to the ambient air. This can be done with strategically placed vents or fans.
Many problems are inherent with the use of heat sinks. Heat sinks are expensive and require a significant amount of labor to install. Obtaining maximum efficiency with a heat sink requires the use of compliant heat transfer material, such as thermal grease, between the second surface of the heat sink and the component. This is necessary to fill in any gaps between the heat sink and the component (the air in such gaps is not a particularly efficient heat transfer medium). The application of compliant heat transfer material to components tends to be costly and time consuming. Further, if vents are required, there is the problem of exposure of the components the outside environment, including contaminants and water, into the chassis. Finally, heat sinks tend to be quite large in comparison to the components that they are cooling, placing unwelcome constraints on package design.
The use of fans is also not without problems. Fans are expensive, increase unit maintenance, consume power, create heat, and generate electrical and acoustic noise. Fans also need access to external air, potentially exposing the unit to the outside environment.
The present inventors have discovered apparatus and methods for dissipating heat in packages which minimizes or eliminates the need for traditional heat sinks and fans.